1. Field of the Invention
The present invention relates to an exposure apparatus for making semiconductor devices and liquid crystal display devices and, in particular, to an XY stage section of such an exposure apparatus.
2. Related Background Art
In order to make semiconductor devices and liquid crystal display devices, there has been employed an exposure apparatus for exposing a photosensitive substrate such as semiconductor wafer or glass plate to a pattern of a reticle or mask (hereinafter referred to as mask). As a means for moving the photosensitive substrate to a predetermined exposure position, the exposure apparatus includes a stage unit equipped with a substrate stage which is movable in two-dimensional directions of X and Y.
FIG. 9 is a conceptual view of a conventional stage unit. A substrate stage 71 having a substrate-mounting surface on its upper side is freely moved, by means of a driving section, over a base 72 along non-depicted guides for XY directions. A photosensitive substrate is mounted on the substrate-mounting surface of the substrate stage 71, and is attached thereto and held thereby as being vacuumed through a vacuum hole (not depicted) formed in the substrate-mounting surface. For such a kind of stage moving mechanism, the technique disclosed in U.S. Pat. No. 4,535,278 can be used.
Connected to the substrate stage 71 are cables for supplying electric power to driving means such as motor disposed within the substrate stage, a coolant pipe for cooling the motor, a coolant pipe for keeping the substrate stage at a predetermined temperature, a vacuum pipe for evacuating the vacuum hole formed in the substrate-mounting surface, and the like (these cables and pipes being collectively referred to as cables hereinafter). These cables 73 are secured to a securing section 73a of the substrate stage 71 and a securing section 73b within the apparatus. As the cables 73 deform between the securing sections 73a and 73b, the substrate stage 71 is allowed to freely move above the base 72.
FIGS. 10 to 12 schematically illustrate various states of the cables 73 when the substrate stage 71 is moved over the base 72. Namely, FIGS. 10 to 12 show states where the substrate stage 71 is positioned at the center, upper left portion, and lower right portion of the base 72, respectively.
When the substrate stage 71 moves from the position shown in FIG. 10 to that shown in FIGS. 11 or 12, while one cable securing section 73a securing the cables 73 moves together with the substrate stage 71, the other cable securing section 73b is kept stationary. Accordingly, as the substrate stage 71 moves, the cables 73 expands and contracts between the two cable securing sections 73a and 73b. Here, as the cables 73 tend to resume their original state, a reaction force 74 indicated by depicted arrow acts on the substrate stage 71 via the cable securing section 73a. Since the direction and magnitude of the reaction force 74 vary depending on the state of expansion and contraction of the cables 73, this reaction force, as disturbance, has adversely affected the positioning accuracy of the substrate stage 71.